In a typical wireless communication network, wireless devices, also known as mobile stations and/or user equipments (UEs), communicate via a Radio Access Network (RAN) to one or more core networks (CN). The RAN covers a geographical area which is divided into cell areas, with each cell area being served by a radio access node such as a base station, e.g., a radio base station (RBS), which in some networks may also be called, for example, a “NodeB” or “eNodeB”. A cell is a geographical area where radio coverage is provided by the radio base station at a base station site or an antenna site in case the antenna and the radio base station are not collocated. Each cell is identified by an identity within the local radio area, which is broadcast in the cell. Another identity identifying the cell uniquely in the whole wireless communication network is also broadcasted in the cell. One base station may have one or more cells. The base stations communicate over the air interface operating on radio frequencies with the wireless devices in downlink (DL) or uplink (UL) transmissions within range of the base stations.
A Universal Mobile Telecommunications System (UMTS) is a third generation mobile communication system, which evolved from the Second Generation (2G) Global System for Mobile Communications (GSM). The UMTS terrestrial radio access network (UTRAN) is essentially a RAN using Wideband Code Division Multiple Access (WCDMA) and/or High Speed Packet Access (HSPA) for wireless devices. In a forum known as the Third Generation Partnership Project (3GPP), telecommunications suppliers propose and agree upon standards for third generation networks and UTRAN specifically, and investigate enhanced data rate and radio capacity. In some versions of the RAN as e.g. in UMTS, several base stations may be connected, e.g., by landlines or microwave, to a controller node, such as a Radio Network Controller (RNC) or a Base Station Controller (BSC), which supervises and coordinates various activities of the plural base stations connected thereto. The RNCs are typically connected to one or more core networks.
Specifications for the Evolved Packet System (EPS) have been completed within the 3rd Generation Partnership Project (3GPP) and this work continues in the coming 3GPP releases. The EPS comprises the Evolved Universal Terrestrial Radio Access Network (E-UTRAN), also known as the Long Term Evolution (LTE) radio access, and the Evolved Packet Core (EPC), also known as System Architecture Evolution (SAE) core network. E-UTRAN/LTE is a variant of a 3GPP radio access technology wherein the radio base stations are directly connected to the EPC core network rather than to RNCs. In general, in E-UTRAN/LTE the functions of a RNC are distributed between the radio base stations, e.g. eNodeBs in LTE, and the core network. As such, the Radio Access Network (RAN) of an EPS has an essentially “flat” architecture comprising radio base stations without reporting to RNCs.
A currently popular vision of the future development of the communication in wireless communication networks comprises huge numbers of small autonomous wireless devices, which typically, more or less infrequently, e.g. once per week to once per minute, transmit and receive only small amounts of data, or are polled for data. These wireless devices are assumed not to be associated with humans, but are rather sensors or actuators of different kinds, which communicate with application servers, which configure the wireless devices and receive data from them, within or outside the wireless communication network. Hence, this type of communication is often referred to as Machine-to-Machine (M2M) communication and the wireless devices may be denoted Machine Devices (MDs). In the 3GPP standardization the corresponding alternative terms are Machine Type Communication (MTC) and MTC devices, with the latter being a subset of the more general term user equipments, UE, or wireless devices. FIG. 1 shows the current state of the 3GPP reference network architecture for Machine Type Communication. In the figure double frame indications for MTC specific entities have been added. Currently the only function that is specified for a Services Capability Server (SCS) is triggering of MTC devices e.g. wireless devices or UEs with a MTC UE application for which an Internet Protocol (IP) address is not available or reachable by the SCS and/or an Application Server (AS). The trigger may cause the MTC device to perform application specific actions that include initiating communication with the SCS or the AS. The SCS may also be regarded as a potential location for future MTC related features. In an indirect model, denoted model 1, the AS is connected to the SCS, which is connected to an MTC-Interworking Function (IWF). The MTC-IWF is connected via a Home Subscriber Server (HSS) to a MTC Authentication, Authorization and Accounting (AAA) server. In the direct model, denoted model 2, the AS is connected to a Gateway GPRS Support Node (GGSN) or Packet Data Network Gateway (P-GW). One may also combine the models into a hybrid model. Control plane is marked with dotted lines and user plane is marked with lines between nodes.
With the nature of MTC devices and the assumed typical uses of the MTC devices follow that MTC devices will often have to be very energy efficient, since external power supplies will often not be available and since it is neither practically nor economically feasible to frequently replace or recharge batteries of the MTC devices. In some scenarios the MTC devices may not even be battery powered, but may instead rely on energy harvesting, i.e. gathering energy from the environment, opportunistically utilizing, the often very limited, energy that may be tapped from sun light, temperature gradients, vibrations, etc.
Random Access Procedure
Before the wireless device may communicate with the wireless communication network, the wireless device have to perform a random access procedure. The random access procedure comprises four actions explained in reference to FIG. 2. Only contention based procedure is shown in FIG. 2.
Action 21: Msg1                The wireless device selects one of the 64 available Random Access Channel (RACH) preambles, or preamble sequences.        The wireless device also needs to give its own identity to the wireless communication network, or the base station, so that wireless communication network can address it in next action. The identity which the wireless device will use is called Random Access-Radio Network Temporary Identity (RA-RNTI). Basically it's not some value sent by the wireless device but interestingly RA-RNTI is determined from a time slot number in which the RACH preamble is sent in a RACH Request.        If the wireless device does not receive any response from the wireless communication network, it increases its power in a fixed step and sends the RACH preamble again.        
Action 22: Msg2                Base station sends “Random Access Response” to the wireless device on Downlink-Shared Channel (DL-SCH) addressed to RA-RNTI calculated from the timeslot in which RACH preamble was sent, as explained in action 21, about RA-RNTI calculation.        The message Random Access Response carries following information:                    Temporary Cell Radio Network Temporary Identity (C-RNTI): base station gives another identity to the wireless device which is called temporary C-RNTI for further communication.            Timing Advance Value: base station also informs the wireless device to change its timing so it can compensate for the round trip delay caused by wireless device distance from the base station.            Uplink Grant Resource: base station will assign initial resource to the wireless device so that the wireless device can use Uplink-Shared Channel (UL-SCH).                        
Action 23: Msg3                Using UL-SCH, the wireless device sends a “RRC connection request message” to the base station, RRC stands for Radio Resource Control.        The wireless device is identified by temporary C-RNTI assigned in the previous action by the base station.        The RRC connection request message comprises following:                    Wireless device identity; e.g. a Temporary Mobile Subscriber Identity (TMSI) or a Random Value,                            TMSI is used if the wireless device has previously connected to the same wireless communication network. With the TMSI value, the wireless device is identified in the core network                The random value is used if the wireless device is connecting for the very first time to wireless communication network. This is because there is a possibility that Temporary C-RNTI has been assigned to more than one wireless device in the previous action, due to multiple requests coming at same time, a Collision scenario will be explained later.                                    Connection establishment cause: shows the reason why the wireless device needs to connect to the wireless communication network.                        
Action 24: Msg4                The base station responds with a contention resolution message to the wireless device whose message was successfully received in action 23. This message is address towards the TMSI value or the random value but contains the new C-RNTI which will be used for further communication.        
Normal Paging Procedure:
When the wireless communication network wants to page a wireless device, the wireless communication network sends a Paging message to all the base stations being a part of a same Tracking Area, or part of a Tracking Area list. The message contains the identity (ID) of the wireless device that the network wants to page. The base station builds a paging message which is transmitted on a Paging Channel (PCH).
The wireless device, listening to the Paging Channel, receives the paging message and tries to establish an RRC connection, by a Random Access procedure as explained in FIG. 2 above.
The wireless communication network then responds to the RACH request, allowing the wireless device to establish an RRC connection. The wireless device will probably receive some data, after which the RRC Connection is not needed and can be released.
The paging procedure is described in more details below with actions related to certain network nodes.
Serving Gateway (S-GW):
    1. DL data arrives for the wireless device at the S-GW.    2. The S-GW creates a DL Data Notification message and forwards the DL Data Notification message to a Mobility Management Entity (MME).Mobility Management Entity (MME):    1. When the wireless device is in EPS Connection Management (ECM)-Idle state, the location is known to the MME on a per Tracking Area (TA) basis. Therefore, the MME has to page all base stations within a group of the TA.    2. The MME starts a timer ‘3413’ when:            a. paging is for Packet Switched (PS) data        b. the wireless device is addressed by System Architecture Evolution (SAE)-TMSI            3. List of Tacking Area Identity (TAI): The MME informs the base station to broadcast the Paging messages in the mentioned TAI's.    4. The MME sends a DL Data Notification Acknowledgement (ACK) message to the S-GW.Base Station:    1. The base station receives a S1 Application Protocol (S1AP) message from the MME indicating paging and the base station constructs an RRC Paging message.    2. The base station generates a paging message that may contain multiple PAGING RECORDS to page multiple wireless devices.Wireless Device:    1. The wireless device wakes up every Paging occasion and searches for Paging (P)-RNTI within a Physical Downlink Control Channel (PDCCH) transmission.    2. If the wireless device finds the P-RNTI then the wireless device proceeds to decode a Physical Downlink Shared Channel (PDSCH) information which is present in the PDCCH.    3. The wireless device decodes the paging message from a PDSCH Resource Block within which the PAGING message is sent.    4. If the wireless device doesn't find its own wireless device identity then the wireless device returns to monitor the Paging Occasion.    5. When the wireless device finds its identity in the message it triggers the Random Access Procedure, as shown in FIG. 2, followed by establishing an RRC Connection.    6. If PAGING is for PS domain then the wireless device Non Access Stratum (NAS) layer triggers a SERVICE REQUEST, otherwise, if the PAGING is for Circuit Switched FallBack (CSFB) then the wireless device triggers an Extended SERVICE REQUEST.
The current Paging procedure as described above, and thus the communication of the wireless device, is too costly for a wireless device, in terms of signalling and therefore also for the battery consumption at the wireless device.